Significant investment has been made in building manufacturing infrastructure for handling glass panel substrates for wafer level fabrication. Such typical manufacturing lines include dedicated machines for glass panel manipulation, glass panel washing, glass panel coating, assembling, etc.
Liquid Crystal Display (LCD) manufacturing is of special interest, where the glass substrates traditionally employed had thicknesses in the order of one millimeter for manufacturing displays intended for home or office use (etc.). The development of mobile devices has created the necessity of using much thinner substrates for mobile displays with thicknesses in the order of a hundred micrometers. Separation gaps between substrates for implementing liquid crystal layers in such mobile displays often are in the order of few micrometers only. In addition, typical feature sizes of such mobile displays are becoming smaller and smaller, e.g., in the order of about 10 micrometers. Many manufacturing processes employed during wafer level display fabrication do not tolerate substrate bend, bubbles and/or other defects. It is often impossible to use currently available equipment in existing manufacturing lines to directly manufacture mobile displays.
Prior attempts to address this miniaturization problem use a carrier substrate to manipulate the required thin substrate during manufacturing.
For example, Asahi Glass Corporation has tried to develop a “carrier glass” technique as shown in FIG. 1A, while Nippon Electric Glass has tried a “glass-on-glass” approach as shown in FIG. 1B. A thin glass substrate, for example 100 micrometer thick, is temporarily attached to a thick carrier glass substrate for providing a combined thick and robust panel. The combined panel can be used in the fabrication of mobile displays using traditional manufacturing lines.
In order to provide the high precision required for mobile displays, the combined carrier (thick) and thin substrates must be laminated (attached) over their entire respective surfaces very uniformly, without bubbles, defects and deformations. In accordance with one prior art proposal, the thin and thick glass substrates are attached together by specific electro static forces over the entire area of the combined panel. In accordance with another prior art proposal, the creation of the combined panel employs a thin adhesive layer, again, dispersed over the entire surface of the combined panel. Because of the very high quality and precision requirements for mobile display applications, the above mentioned approaches are costly.
After the wafer level fabrication is complete, the thick carrier glass substrate is delaminated (detached) and the remaining display is thin and of reduced weight (light). However, specialized equipment must be used for the delamination (detachment) of the carrier glass substrate depending on the technology used to attach the thin glass substrate and the thick carrier glass substrate together.